The present invention relates to chainrings, and in particular, one embodiment contemplates solitary chainrings for use with a known chain in a bicycle drivetrain system which comprises a bicycle crank.
Bicycles and other chain-driven vehicles generally use one or more chainrings mounted to a crank arm and a set of sprockets which are mounted on a rear hub and are connected to the chainring via a chain. Various mechanisms are used for holding the chain on the chainring and the sprocket in use. These mechanisms comprise chain guards, chain tensioners, chain watchers, rear derailleur arrangements and the like.
When riding a bicycle with a chain-driven drive train, the handling of the chain and the chainring engagement is particularly important for a safe and effective drive of the bicycle. Keeping the chain in engagement with the chainring may be difficult. In particular, in bicycles with gear-shifting devices, considerable changes in the chain tension and dynamic movements of the chain can occur, above all when riding off-road.
Furthermore, in each bicycle the chainring may touch the chain stay of the bicycle frame if the crank is in a position in which high loads are exerted by the rider, which causes an elastic deformation of the bicycle frame and the crank arrangement. This can lead to damage to the frame and to the chainring and can cause other problems.
From the prior art a plurality of chainrings, but also sprockets, is known, wherein the teeth are deformed locally in order to facilitate upshifts or in order to improve the chain guiding characteristics.
Reference is made for example to the document WO 98/06962 A1, in which the teeth are in zigzag form or offset in an undulating form along the circumferential direction in order to avoid rattling of the chain. A similar solution is known from the document FR 2 545 902 A1 and from the document DE 28 16 137 A.
The document EP 0 934 871 B1 shows a sprocket arrangement in which individual sprockets have been machined to remove material in order to avoid build-up of dirt and to facilitate upshifts for the chain during gear-shifting operations.
The document U.S. Pat. No. 3,745,851 shows a chain wheel in which the teeth are broadened by deformations in the region of the tooth flanks.
The document U.S. Pat. No. 3,654,814 shows a solution in which oval bead-like protrusions are provided on both sides of the teeth.
Finally the document U.S. Pat. No. 4,867,733 shows a chain wheel in sandwich construction which is produced in its central region from an elastic body which is in each case surrounded laterally by metal plates forming the individual teeth. Additionally, if need be lateral buffer elements are provided.
On the one hand the prior art described above has disadvantages, in particular because the manufacture is complex and therefore expensive, and moreover is subject to the problem that the required chain guiding characteristics cannot be reliably and permanently set.
The object of the invention is to provide a chainring which enables improved handling of the drive chain, in particular for bicycles which are ridden successfully and reliably on rough and demanding ground, wherein the production of the chainring according to the invention takes place simply and cost-effectively with high functionality and long service life of the chainring.